It is a widely known fact that hand-held blenders of the type referred to by the present invention have a motor assembly that includes an electric motor that can be electrically powered and which constitutes the drive part, with an output shaft, and a tool shank that, when correctly coupled to said motor assembly, allows the movement of the motor to be transmitted to the proximal end of the shaft that runs along the length of said shank, and which on its opposite end, or distal end, has a blade or similar device for cutting and blending the food to which it is applied or the desired blending operation.
As will be understood, it is necessary for the coupling between the tool shank and the motor assembly to have characteristics that guarantee sufficient safety conditions during its use, but which also allow the tool shank to be released, i.e. allow the tool shank to be separated from the motor assembly when the user desires, with a view to subjecting the former to the necessary operations to keep it in good conditions of hygiene and cleanliness, in addition to any other maintenance operation, repair of any component, or even replacement of the tool shank in the event of it breaking or suffering irreparable damage.
The normal connection between a tool shank and motor assembly in a blender of the type considered here currently consists of the provision of a screw or bayonet type connection. Screw and bayonet connections can be designed in such a way that they are more or less easy to engage/disengage. However, both types of coupling, assembly and fastening have certain drawbacks in practice, because if these connections are performed in such a way that they are easy to engage/disengage, they occasionally present the problem that they accidentally become disengaged while the blender is in use, which clearly represents a hazard for the user; on the other hand, if the coupling is performed in such a way that it is difficult for the user to engage/disengage, this presents a different set of problems, as releasing the tool shank would mean applying excessive force, therefore making it impossible for the user to separate the two parts.
Bearing in mind the drawbacks that exist in the current state of the art with regard to said hand-held blenders, in particular with respect to engaging/disengaging the tool shank and the motor assembly, the main objective proposed by the present invention is to design a coupling that allows the user to perform the coupling or releasing operation easily, conveniently and quickly, yet at the same time with absolute certainty that the connection between the two parts is stable, without the possibility of accidental separation while it is in use, and with the user's full knowledge that the connection has finally been correctly established.
This objective has been fully achieved by the releasable coupling device of the invention, which will be explained below, and the characteristics of which are contained in the characterizing part of the attached claim 1.
Essentially, the coupling device proposed by the present invention is connected to the screw connection habitually used in this type of blenders between the components of the inner nut on the bell at the top of the tool shank and the cylindrical projection or nozzle that extends outwards from the end base of the motor assembly surrounding and protecting the drive shaft that is connected to the motor, said screw connection corresponding to a design of the quick coupling type, with the particularity that the motor assembly additionally includes, in a position radially outside said cylindrical nozzle, the provision of a cylindrical formation inside which the effective means of retention is housed, which consists of a retaining ball that projects through the mouth of said formation, said ball being pushed outwards by a spring housed inside the same formation. Complementing this arrangement, the bell piece of the tool shank, in addition to having a threaded section on its coupling nut that can fit with the threaded section formed on the outer surface of the output nozzle of the motor assembly, has its internal space divided into segments by means of radial partitions, one of these partitions having an integral housing of a semispherical shape whose overall diameter and dimensions are complementary to those of the retaining ball included in the formation of the blender's motor assembly, so that with the coupling between the motor assembly and the tool shank by screwing the nut of the bell onto the cylindrical nozzle of the motor assembly, as the two pieces successively approach one another, the ball comes into contact with the integral housing on the rib of the bell, and after giving elastically against the action of the spring, thanks to the recovery of the spring the ball is finally housed inside the housing when the two pieces are sufficiently aligned with one another, the action of which makes a sound indicating to the user that the effective coupling of the two components has occurred.
As will be understood, the characteristics of the spring are such that they push the ball with an expanding force that is sufficient to ensure a firm and secure connection between the pieces, which prevents the undesired detachment of the motor assembly and the tool shank, whilst its strength is such that it allows the user to detach the two pieces when desired without the need to apply excessive force or other drawbacks.